Yesterday during AMD's Q2'06 earnings conference call, AMD's
President and Chief Operating Officer Dirk Meyer recapped the long term plans
for the company. Although the bulk of his comments were already stated in
during the June AMD
Analyst's Day, Meyer also added the tidbit that the company plans "to
demonstration our next-generation processor core, in a native quad-core
implementation, before the end of the year." Earlier this year, AMD's Executive Vice President Henri Richard claimed this native-quad core processor would be called K8L.

Earlier AMD roadmaps have revealed that quad-core production CPUs would not
utilize a native quad-core design until late 2007 or 2008. To
put that into perspective AMD demonstrated the first dual-core Opteron samples
in August 2004, with the processor tape out in June 2004. The official launch
of dual-core Opteron occurred on April 21, 2005. On the same call Meyer
announced that that the native quad-core would launch in the middle of 2007 -- suggesting the non-native quad-core Deerhound designs may come earlier than expected or not at all.

> "Ummm...how could you possibly know about diminishing returns on a system that isn't built yet? "

From the same way one knows about the performance of any processor before it's built-- software simulation.

> "the more cores you have the BETTER your returns... "

You don't understand what's meant by diminishing returns. If you add cores, your performance rises...but by a ever-diminishing amount.

The Intel sims showed Mitosis achieving about a 2.5X speedup on a 4X system, with slightly more than half of that gain due simply to the side-effect of the other cores increasing the cache hits of the primary, from prerequesting data. That's pretty good scaling, but at 8 cores, the results are less impressive---about a 3.5X speedup. I didn't see any 16-core sims, but with that type of curve, it'd probably work out to just under 4X...which means you're only achieving 25% theoretical efficiency.

quote: From the same way one knows about the performance of any processor before it's built-- software simulation

How can you do a software simulation when the Mitosis Compiler is nowhere near finished? Mitosis is predominantly a software driven enhancement...

quote: at 8 cores, the results are less impressive---about a 3.5X speedup

Well, if you're looking at the same data I am (and it sounds like you are), then it's based on an early version of the Mitosis Compiler (Alpha version) from 2005...
Remember that they are still in the "proof of concept" phase for Mitosis, so you shouldn't expect it to look anything like the final product.

> " it's based on an early version of the Mitosis Compiler (Alpha version) from 2005..."

Not even an "alpha" version...just a research proof of concept. But the point is their simulations show a definite ceiling for the performance benefits of speculative threading. Of course, you could always postulate a breakthrough in basic theory-- but given what we know today, Mitosis isn't going to utilize more than 4-8 cores for a single-threaded process.